The BF gas in dry dedusting technology of blast furnace gas is dedusted primarily by a gravity dust removal system, and then enters a bag precipitator for secondary dedusting; afterwards, the purified gas enters the TRT for decompression and used to drive the generator to generate power. Compared with the wet dedusting method of scrubber, venturi tube and double venturi tube, blast furnace gas dry dedusting technology has a great advantage, namely, high purification efficiency, significant reduction of water consumption, more importantly, greatly improving electric energy generated by TRT, increasing energy recovery and utilization and decreasing energy consumption for each ton of iron.
With the development of iron and steel industry in China, especially the increase in production cost, cheap iron ores have attracted attention and have gradually been utilized. The high content of trace elements, especially harmful elements in cheap iron ores, particularly the increase of chlorine contents entering the blast furnace, leads to the rising of HCl content in blast furnace gas, aggravating the corrosion of pipes and equipment. In recent years, metal members such as blast furnace gas pipes and TRT blades in various iron & steel enterprises are eroded by HCl to different extents. As a result, one of the most critical issues in metallurgical field is to study the removal of HCl in blast furnace gas under dry dedusting conditions.
A number of studies on HCl removal have been made in the fields of integrated gasification combined cycle (IGCC), molten carbonate fuel cell (MCFC), petrochemical and waste incineration; for example, with the fixed bed technology, the dechlorinating agent used is mostly alkaline dechlorinating agent, including lime-based (limestone, slaked lime and quick lime) and sodium-based (soda powder and baking soda) dechlorinating agent. However, due to the unique properties of blast furnace gas such as rapid flow rate, large flow amount, high pressure, high content of CO2, water vapor and dust, these processes and technologies are not suitable to BG gas.
Based on the study above and in view of the characteristics of blast furnace top gas, this invention discloses a dechlorinating agent featuring low cost, good dechlorination effect that is capable of being fully applied in blast furnace top gas.